Multiple stacked capacitors formed within an opening with thick capacitor dielectric

ABSTRACT

For forming stacked capacitors, an opening is formed through at least one semiconductor material. A lower electrode material is patterned within the opening to form a plurality of lower electrodes within the opening. The stacked capacitors are formed with the lower electrodes within the opening by depositing a capacitor dielectric and an upper electrode within the opening. With such a relatively large opening, a capacitor dielectric of the stacked capacitors is deposited with a large thickness for improving reliability of the stacked capacitors.

The present application is a divisional of an earlier filed copendingpatent application with Ser. No. 10/997,408 filed on Nov. 24, 2004, forwhich priority is claimed. This earlier filed copending patentapplication with Ser. No. 10/997,408 is in its entirety incorporatedherewith by reference.

The present application also claims priority under 35 U.S.C. §119 toKorean Patent Application No. 2004-0007305, filed on Feb. 4, 2004, whichis incorporated herein by reference in its entirety. A certified copy ofKorean Patent Application No. 2004-0007305 is contained in the parentcopending patent application with Ser. No. 10/997,408.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to stacked capacitors, and moreparticularly to forming multiple stacked capacitors within a relativelylarge opening with thick capacitor dielectric.

2. Description of the Related Art

Capacitors are widely used for storing data by charge retention, asknown to one of ordinary skill in the art. For example, a DRAM (dynamicrandom access memory) cell and a ferroelectric memory cell each use acapacitor for such data storage.

Integrated circuits are desired to be fabricated ever more densely. Onthe other hand, the capacitance of an integrated circuit capacitordecreases with size reduction of the capacitor. Such lower capacitancedegrades the sensing margin during read of data stored in a memory cell.

Thus, the capacitance of the capacitor is desired to be increased forsmaller area of the capacitor. To that end, the dielectric constant ofthe capacitor dielectric between two electrodes is increased for in turnincreasing the capacitance. Alternatively, a stacked capacitor is formedwith increased overlap between two electrodes formed with increasedheight for increased capacitance.

One example of such a stacked capacitor is disclosed in U.S. Pat. No.6,559,497 as illustrated in the cross-sectional view of FIG. 1.Referring to FIG. 1, a first oxide layer 11 is formed on a semiconductorsubstrate 10. A conductive plug 12 is formed through the first oxidelayer 11 to contact a predetermined region of the semiconductorsubstrate 10.

In addition, a second oxide layer 13 is formed to cover the first oxidelayer 11 and the conductive plug 12. A hole 14 is formed through thesecond oxide layer 13 to expose the conductive plug 12. A conformallower electrode 15 is disposed on inner sidewalls and a bottom surfaceof the hole 14. A conformal capacitor dielectric 16 covers the lowerelectrode 15. An upper electrode 17 is disposed on the capacitordielectric and fills the hole 14. The upper and lower electrodes 15 and17 and the capacitor dielectric 16 form the stacked capacitor.

In the prior art stacked capacitor of FIG. 1, the lower electrode 15 isconformally deposited onto the inner sidewall(s) and the bottom wall ofthe hole 14 for increasing the area of overlap between the electrodes 15and 17. In addition, the capacitor dielectric 16 is a high-k dielectric(i.e., a dielectric having a dielectric constant higher than that ofsilicon dioxide SiO₂). Such increased area of overlap and such a high-kcapacitor dielectric 16 increase the capacitance of the stackedcapacitor.

However, as integrated circuits are fabricated more densely, the aspectratio of the hole 14 is increased. For ensuring that the upper electrode17 properly fills the hole 14 without a void, the lower electrode 15 andthe capacitor dielectric 16 are formed to be as thin as possible. Forexample, the total thickness of the lower electrode 15 and the capacitordielectric 16 is smaller than half of the width of the hole 14 forensuring that the upper electrode 17 properly fills the hole 14.

With such a thin capacitor dielectric 16, leakage current between theelectrodes 15 and 17 may increase, for degradation of data stored in thecapacitor. On the other hand, with a thicker capacitor dielectric 16,the upper electrode 17 may not properly fill the hole 14 with voidformation leading to decreased overlap and in turn decreased capacitancebetween the two electrodes 15 and 17.

In addition, the capacitor dielectric 16 may be comprised of aferroelectric material as disclosed in U.S. Pat. No. 6,559,497. As knownto one of ordinary skill in the art, a ferroelectric material ispolarized to a predetermined direction according to the intensity anddirection of an external electric field. Furthermore, a hysteresisphenomenon maintains the polarized state of the ferroelectric materialeven after the external electric field is removed. Thus, a ferroelectricmemory device with the ferroelectric material has a nonvolatilecharacteristic from the polarization hysteresis for maintaining storeddata even when power is cut off.

However, if the thickness of the capacitor dielectric 16 comprised of aferroelectric material is reduced, the polarization hysteresis of thecapacitor dielectric 16 may be deteriorated. For example, if thethickness of the capacitor dielectric 16 is less than about 500 Å, thecapacitor dielectric 16 may not maintain the polarization hysteresis. Inthat case, a ferroelectric memory device formed with the stackedcapacitor loses the nonvolatile characteristic.

Nevertheless, the width of the hole 14 and thus the thickness of thecapacitor dielectric 16 of the prior art stacked capacitor of FIG. 1 isdesired to be further decreased for higher integrated circuit density.Such decreased thickness of the capacitor dielectric 16 deterioratesreliability of the semiconductor device formed with the stackedcapacitor of FIG. 1.

Thus, a mechanism is desired for forming stacked capacitors with alarger thickness of the capacitor dielectric even in densely fabricatedintegrated circuits.

SUMMARY OF THE INVENTION

Accordingly, a plurality of stacked capacitors is formed within arelatively large opening of an integrated circuit. With such arelatively large opening, the capacitor dielectric is deposited with alarge thickness for improving reliability of the stacked capacitors.

In a general aspect of the present invention, for forming a plurality ofstacked capacitors, an opening is formed through at least onesemiconductor material. A lower electrode material is patterned withinthe opening to form a plurality of lower electrodes within the opening.The stacked capacitors are formed with the lower electrodes within theopening.

In one embodiment of the present invention, the opening is formedthrough a capping layer and a molding layer that are each comprised ofan insulating material deposited over a semiconductor substrate.

In another embodiment of the present invention, each of the lowerelectrodes includes a respective support part disposed over a respectiveconductive plug, and includes a wall part disposed along a respectiveportion of at least one wall of the opening. In a further embodiment ofthe present invention, at least one sidewall of the opening is formed tobe inclined.

For patterning the lower electrodes in another embodiment of the presentinvention, the lower electrode material is conformally deposited on atleast one wall of the opening. The lower electrode material is patternedin a photolithography process for forming the lower electrodes.

In an example embodiment of the present invention, the photolithographyprocess includes an isotropic (non-directional) etch when the lowerelectrodes are formed on at least one non-inclined sidewall of theopening. In an alternative embodiment of the present invention, thephotolithography process includes an anisotropic (directional) etch whenthe lower electrodes are formed on at least one inclined sidewall of theopening.

In another embodiment of the present invention for forming the stackedcapacitors, a capacitor dielectric is deposited on the lower electrodes,and an upper electrode is formed on the capacitor dielectric. In anexample embodiment of the present invention, the capacitor dielectric iscomprised of one of a high-K dielectric or a ferroelectric material.

In a further embodiment of the present invention, the upper electrode iscontinuous over a plurality of openings, with each opening having arespective plurality of stacked capacitors formed therein. In analternative embodiment of the present invention, the upper electrode iscontinuous over a column of stacked capacitors formed through aplurality of openings.

In another embodiment of the present invention, an upper insulatinglayer is deposited over the upper electrode. An interconnect plug isformed through the upper insulating layer within the opening to becoupled to the upper electrode. In an alternative embodiment of thepresent invention, the interconnect plug is formed through the upperinsulating layer outside of the opening over a mold layer to be coupledto the upper electrode.

In a further embodiment of the present invention, when the opening isformed through the capping layer and the molding layer, the lowerelectrodes, the capacitor dielectric, and the upper electrode areplanarized down to the capping layer to be contained within the opening.In an alternative embodiment of the present invention, the lowerelectrodes, the capacitor dielectric, and the upper electrode are formedover a portion of the capping layer.

In another embodiment of the present invention, the opening is filledwith an upper insulating layer or with the upper electrode.

In an example embodiment of the present invention, the opening has asquare shape, and each lower electrode is formed at a respective cornerof the opening. In another example embodiment of the present invention,the opening has a groove shape, and the lower electrodes are formedalong sides of the opening.

In this manner, the stacked capacitors are formed within a relativelylarge opening with a low aspect ratio such that the capacitor dielectricmay be deposited with a higher thickness. Such a higher thickness of thecapacitor dielectric results in higher reliability of the stackedcapacitors.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and advantages of the present invention willbecome more apparent when described in detailed exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a cross-sectional view of a stacked capacitor of the priorart;

FIG. 2 is a top view of stacked capacitors formed within a relativelylarge opening, according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view along line I-I′ in FIG. 2;

FIG. 4 is an isometric view of lower electrodes of the stackedcapacitors of FIG. 2;

FIG. 5 is a top view of stacked capacitors with change of location ofupper electrodes of the stacked capacitors, according to anotherembodiment of the present invention;

FIG. 6 is a cross-sectional view along line II-II′ in FIG. 5;

FIG. 7 is a top view with modification of upper electrodes of thestacked capacitors according to another embodiment of the presentinvention;

FIG. 8 is a cross-sectional view along line I-I′ of FIG. 2 illustratingplanarization of the stacked capacitors according to another embodimentof the present invention;

FIGS. 9A through 12A are top views illustrating steps for fabricatingthe stacked capacitors of FIG. 2, according to an embodiment of thepresent invention;

FIGS. 9B through 12B are cross-sectional views along line III-III′ ofFIGS. 9A through 12A, respectively;

FIGS. 13A through 15A are top views illustrating steps for fabricatingthe stacked capacitors of FIG. 8, according to an embodiment of thepresent invention;

FIGS. 13B through 15B are cross-sectional views along line IV-IV′ inFIGS. 13A through 15A, respectively;

FIG. 16 is a top view of stacked capacitors formed within an openinghaving a groove shape, according to another embodiment of the presentinvention;

FIG. 17 is a cross-sectional view along line V-V′ in FIG. 16;

FIG. 18 is an isometric view of lower electrodes of the stackedcapacitors of FIG. 16;

FIG. 19 is a top view with square-shaped upper electrodes along thegroove-shaped opening, according to another embodiment of the presentinvention;

FIG. 20 is a cross-sectional view along line V-V′ in FIG. 16 withplanarization of the stacked capacitors, according to another embodimentof the present invention;

FIGS. 21A and 22A are top views illustrating steps for fabricating thestacked capacitors of FIG. 16 according to an embodiment of the presentinvention;

FIGS. 21B and 22B are cross-sectional views along line VI-VI′ in FIGS.21A and 22A, respectively;

FIG. 23A is a top view and FIG. 23B is a cross-sectional view along lineVII-VII′ in FIG. 23A, for illustrating fabrication of the stackedcapacitors of FIG. 20, according to an embodiment of the presentinvention.

The figures referred to herein are drawn for clarity of illustration andare not necessarily drawn to scale. Elements having the same last twodigits of reference numbers in FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9A, 9B,10A, 10B, 11A, 11B, 12A, 12B, 13A, 13B, 14A, 14B, 15A, 15B, 16, 17, 18,19, 20, 21A, 21B, 22A, 22B, 23A, and 23B refer to elements havingsimilar structure and/or function.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 is a top view of stacked capacitors formed according to anembodiment of the present invention. FIG. 3 is a cross-sectional viewalong line I-I′ in FIG. 2. FIG. 3 is an isometric view of lowerelectrodes of the stacked capacitors of FIG. 2.

Referring to FIGS. 2, 3, and 4, a lower insulating layer 102 and an etchstop layer 104 are deposited sequentially on a semiconductor substrate100. Contact holes 105 are etched through the etch stop layer 104 andthe lower insulating layer 102 to expose regions of the substrate 100.The contact holes 105 are disposed along rows and columns over thesubstrate 100.

In addition, a respective contact plug 106 and a respective oxygenbarrier pattern 108 fill each contact hole 105. The present inventionmay also be practiced with the oxygen barrier pattern 108 omitted. Arespective source/drain of a field effect transistor (not shown) may bein the substrate 100 under each contact plug 106 for forming arespective DRAM (dynamic random access memory) cell in one exampleembodiment of the present invention.

The lower insulating layer 102 is comprised of silicon dioxide (SiO₂),and the contact plugs 106 are comprised of doped polysilicon or otherconductive material such as a metal, in one embodiment of the presentinvention. For example, the contact plugs 105 are comprised of tungsten,or a metal nitride such as titanium nitride or tantalum nitride, or ametal silicide such as tungsten silicide, in an example embodiment ofthe present invention.

The oxygen barrier pattern 108 is comprised of a conductive materialthat prevents oxygen from reaching the conductive plug 105. For example,the oxygen barrier pattern 108 is comprised of a metal nitride such astitanium nitride or tantalum nitride, or a conductive metal oxide suchas iridium oxide, in an example embodiment of the present invention.

A mold layer 110 covers the etch stop layer 104 and the oxygen barrierpatterns 108. A capping layer 112 is disposed on the mold layer 110. Themold layer 110 is comprised of silicon dioxide (SiO₂), in one embodimentof the present invention. The etch stop layer 104 is comprised of aninsulating material having etch selectivity from the mold layer 110.

A plurality of storage openings 115 are formed through the capping layer112 and the mold layer 110. The storage openings 115 are formed alongrows and columns, in one embodiment of the present invention.

Each storage opening 115 exposes a plurality of neighboring oxygenbarrier patterns 108. In FIG. 2 for example, each storage opening 115exposes an array of four neighboring oxygen barrier patterns 108disposed along two rows and two columns. Further in FIG. 2, each storageopening 115 has a square shape with four inner corners, with each cornerdisposed outside a respective one of the four exposed oxygen barrierpatterns 108.

A respective lower electrode 125 is disposed on each of the four oxygenbarrier patterns 108 within the opening 115. Each lower electrode 125includes a respective support part 122 and a respective wall part 123.The respective support part 122 contacts a top surface of an oxygenbarrier pattern 108, and the respective wall part 123 extends upwardalong sidewalls of a respective corner of the opening 115. In theembodiment of FIGS. 2 and 4, the four lower electrodes 125 aresymmetrically formed at the four corners with respect to a center partof the square opening 115.

A top portion of the wall part 123 extends laterally over a top surfaceof the capping layer 112 in the embodiment of FIGS. 3 and 4. Further inthe embodiment of FIGS. 2, 3, and 4, the lower electrodes 125 areseparated and electrically insulated from each other.

The lower electrodes 125 are comprised of a noble metal such as iridium(Ir), ruthenium (Ru), or platinum (Pt), in an example embodiment of thepresent invention. In addition, the lower electrodes 125 may furtherinclude an adhesion layer and/or a barrier layer. For example, anadhesion layer comprised of titanium or tantalum may be included in astack of layers forming the lower electrodes 124. In addition, a barrierlayer comprised of a metal nitride such as titanium nitride, tantalumnitride, aluminum silicon nitride, or tungsten nitride, may be includedin the stack of layers forming the lower electrodes 125.

The adhesion layer would be formed for enhancing adhesion of the noblemetal of the lower electrodes 125 to underlying material. The barrierlayer would prevent oxygen from reaching an interface between the lowerelectrode 125 and the buried contact plug 106. In that case, the oxygenbarrier pattern 108 may be omitted.

Further referring to FIGS. 2 and 3, a capacitor dielectric 127 isconformally deposited with relatively high thickness over the lowerelectrodes 125. The capacitor dielectric 127 is comprised of a high-kdielectric having a dielectric constant larger than that of silicondioxide (SiO₂), in one embodiment of the present invention. For example,the capacitor dielectric 127 is comprised of aluminum oxide, hafniumoxide, titanium oxide, or a combination thereof.

Alternatively, the capacitor dielectric 127 is comprised of aferroelectric material such as SrTiO₃, BaTiO₃, BST, PZT,SBT(SrBi₂Ta₂O₉), PLZT((Pb,La)(Zr,Ti)O₃), ((Pb,Ca)(Zr,Ti)O₃), Bi₄Ti₃O₁₂,BLT(BiLaTiO₃), or a combination thereof. When the capacitor dielectric127 is formed of PZT, the etch stop layer 104 and the capping layer 112are comprised of an insulating material such as TiO₂ that stimulatesgrowth of PZT crystal. TiO₂ not only has etch selectivity with respectto silicon dioxide but also stimulates the growth of PZT. If thecapacitor dielectric 127 is comprised of the above material except PZT,the etch stop layer 104 may be comprised of silicon nitride, and thecapping layer 112 may be comprised of silicon nitride or not be formed.

Further referring to FIGS. 2 and 3, an upper electrode 130 a is disposedon the capacitor dielectric 127 and over the lower electrodes 125. Theupper electrode 130 a is disposed over both of the wall part 123 and thesupport part 122 of the lower electrodes 125. In the embodiment of FIG.2, each upper electrode 130 a is disposed over the respective four lowerelectrodes 125 within a respective opening 115. Alternatively, eachupper electrode 130 a is disposed over all the lower electrodes 125 in acell block (not shown) of the substrate 100.

In any case, the upper electrodes 130 a are separate and electricallyisolated from each other. The upper electrodes 130 a are arranged alongrows and columns in an embodiment of the present invention. Referring toFIG. 3, a top portion of the upper electrode 130 a protrudes laterallyto overlap the capping layer 112. The upper electrode 130 a is comprisedof a noble metal such as iridium (Ir), ruthenium (Ru) or platinum (Pt)or the like. The upper electrode 130 a is conformal on top of underlyingstructures in an embodiment of the present invention.

Each stacked capacitor in FIGS. 2, 3, and 4 is comprised of a respectivelower electrode 125, a respective capacitor dielectric 127, and arespective upper electrode 130 a. In the embodiment of FIG. 2, fourstacked capacitors are formed with the four lower electrodes 125 withineach storage opening 115. Each storage opening 115 has an integralcapacitor dielectric 127 and an integral upper electrode 130 a formedtherein for forming the four stacked capacitors in the embodiment ofFIGS. 2, 3, and 4.

An upper insulating layer 132 is blanket deposited to cover the upperelectrodes 130 a. When the upper electrodes 130 a are conformal, theupper insulating layer 132 fills the storage opening 115. In an exampleembodiment of the present invention, the upper insulating layer 132includes an encapsulating layer (not illustrated) covering the upperelectrodes 130 a. The encapsulating layer prevents degradation of theupper electrodes 130 a and the capacitor dielectric 127 and is comprisedof Al₂O₃, TiO₂, or a combination thereof for example.

Interconnection contact holes 133 are formed through the upperinsulating layer 132 to expose regions such as centers of the upperelectrodes 130 a. A respective interconnection plug 134 fills each ofthe interconnection contact holes 133 to contact a respective upperelectrode 130 a. Interconnections 135 are disposed on the upperinsulating layer 132 to couple the interconnection plugs 134 along acolumn. Each interconnection 135 corresponds to a plate line when thestacked capacitors are used within a ferroelectric memory device.

Alternatively, an upper electrode 130 a may be formed continuously overa column of stacked capacitors through a column of storage openings 115.In that case, each upper electrode 130 a corresponds to a plate line ofa ferroelectric memory device, and the interconnection plugs 134 and theinterconnections 135 may be omitted.

FIGS. 5 and 6 illustrate formation of stacked capacitors according toanother embodiment of the present invention. FIG. 5 is a top view ofstacked capacitors formed according to this alternative embodiment ofthe present invention. FIG. 6 is a cross-sectional view along lineII-II′ in FIG. 5.

Referring to FIGS. 5 and 6, each upper electrode 130 b is disposed overan intervening portion of mold layer 110 between two adjacent storageopenings 115 to cover the lower electrodes 125 at the sidewalls of theintervening mold layer 110. Referring to FIG. 5, each upper electrode130 b covers an array of four lower electrodes 125 disposed around theintervening portion of the mold layer 110.

Thus, the center of the upper electrode 130 b is over the interveningmold layer 110. As a result, portions of two upper electrodes 130 b areplaced in one storage opening 115. In FIG. 5, the upper electrodes 130 bare still disposed along rows and columns over the substrate 100.

Referring to FIG. 6, an interconnection contact hole 133′ is formedthrough the upper insulating layer 132 to expose a region of each of theupper electrodes 130 b on the intervening mold layer 110. Therefore, thedepth of the interconnection contact hole 133′ is reduced to decrease anaspect ratio thereof for easier formation of the interconnection contacthole 133′. The interconnection plug 134′ fills the interconnectioncontact hole 133′, and interconnections 135′ are disposed on the upperinsulating layer 132 to connect the interconnection plugs 134′.

Alternatively, if each upper electrode 130 b is continuous along acolumn of storage openings 115, the interconnection plugs 134′ and theinterconnections 135′ may be omitted. In another embodiment of thepresent invention, as illustrated in FIG. 7, each upper electrode 130 chas a line-shape that extends over a column of lower electrodes 125.When the stacked capacitors of FIG. 7 form a ferroelectric memorydevice, intrinsic capacitance between neighboring stacked capacitors isreduced in the embodiment of FIG. 7.

With such stacked capacitors of FIGS. 2, 3, 4, 5, 6, and 7, each storageopening 115 holds a plurality of stacked capacitors and thus is largerthan an opening holding one stacked capacitor of the prior art. Withsuch a large opening 115, the capacitor dielectric 127 may be formedwith a relatively large thickness to reduce leakage current between thelower and upper electrodes of the stacked capacitors and to preserve thepolarization hysteresis of the capacitor dielectric 127 comprised of aferroelectric material. Furthermore with such a large opening 115, theupper electrodes 130 a, 130 b, or 130 c overlap the lower electrodes 125even for a large thickness of the capacitor dielectric 127.

Additionally with such a large opening 115, the height of the wall part123 of the lower electrodes 125 is increased within acceptable aspectratio of the opening 115 for in turn increasing the area and thus thecapacitance of the stacked capacitors. Overlap between the lowerelectrode 125 and the upper electrode 130 a over a portion of thecapping layer 112 further increases area and thus capacitance of thestacked capacitors.

Alternatively, the upper and lower electrodes of the stacked capacitorsare planarized with respect to the capping layer 112 to be containedwithin the opening 115 as illustrated in the cross-sectional view ofFIG. 8. Referring to FIG. 8, a wall part 123′ of the lower electrodes125′, the capacitor dielectric 127 a, and the upper electrode 130 a havebeen polished away in a CMP (chemical mechanical polish) process fromthe top surface of the capping layer 112 to be contained within theopening 115. Other-wise, the stacked capacitors of FIG. 8 are similar tothose of FIG. 3.

Further referring to FIG. 8, a buffer insulating material 140 a isdisposed on the upper electrode 130 a′ to fill the storage opening 115.The buffer insulating material 140 a is also planarized to the secondcapping layer 112 to be contained within the storage opening 115,Alternatively, the upper electrode 130 a′ fills the storage opening 115,and the buffer insulating material 140 a is omitted in that case.

Referring to FIG. 8, an upper insulating layer 132′ covers the aboveresultant structure. An interconnection plug 134″ fills aninterconnection contact hole 133″ formed through the upper insulatinglayer 132′ and the buffer insulating material 140 a to contact the upperelectrode 130 a′. The interconnection 135″ is disposed on the upperinsulating layer 132′ to contact the interconnection plug 134″.

Further referring to FIG. 8, an encapsulating layer (not shown) may beformed as part of the buffer insulating material 140 a and/or the upperinsulating layer 132′ to cover the lower electrode 125′, the capacitordielectric 127 a, and the upper electrode 130 a′. The encapsulatinglayer is comprised of Al₂O₃, TiO₂, or a combination thereof, in anembodiment of the present invention.

In the embodiment of FIG. 8, the lower electrodes 125′, the capacitordielectric 127 a, the upper electrode 130 a′, and the buffer insulatingmaterial 140 a are planarized to be contained within the opening 115.Such a resulting flat step coverage allows for easier subsequentdeposition of integrated circuit materials thereon for improvingfabrication yield.

FIGS. 9A through 12A are top views illustrating steps for fabricatingthe stacked capacitors of FIG. 3, according to an embodiment of thepresent invention. FIGS. 9B through 12B are cross-sectional views alongline III-III′ of FIGS. 9A through 12A, respectively.

Referring to FIGS. 9A and 9B, the lower insulating layer 102 and theetch stop layer 104 are sequentially deposited on the substrate 100. Inaddition, the etch stop layer 104 and the lower insulating layer 102 arepatterned to form the contact holes 105 over regions of the substrate100. The contact holes are arranged along rows and columns over thesubstrate 100.

The respective contact plug 106 is formed to fill each contact hole 105and is comprised of a conductive material such as doped polysilicon ortungsten or of a metal nitride such as titanium nitride or tantalumnitride, in one embodiment of the present invention. An upper portion ofeach contact plug 106 is recessed using an etch back process, and theoxygen barrier pattern 108 is formed therein. The oxygen barrier pattern108 is comprised of a conductive material that prevents oxygenpenetration, for example a metal nitride such as titanium nitride (TiN),tantalum nitride (TaN) or aluminum silicon nitride (AlSiN), in oneembodiment of the present invention. The present invention may bepracticed with or without formation of the oxygen barrier pattern 108.

Thereafter, the mold layer 110 and the capping layer 112 aresequentially blanket deposited over the substrate 100. The lowerinsulating layer 102 and the mold layer 110 are comprised of silicondioxide (SiO₂) in one embodiment of the present invention. The etch stoplayer 104 is comprised of an insulating material having etch selectivityfrom the mold layer 110.

The capping layer 112 and the mold layer 110 are patterned to form theplurality of storage openings 115. Each storage opening 115 exposes therespective plurality of the oxygen barrier patterns 108. For example,each storage opening 115 exposes an array of four oxygen barrierpatterns 108 as illustrated in FIG. 9A. In addition in FIG. 9A, eachexposed oxygen barrier pattern 108 is disposed adjacent a respectivecorner of the storage opening 115 that is square-shaped. FIG. 9Aillustrates the buried contact hole 105 and the storage opening 115 assquare-shaped, but the present invention may also be practiced when thecorners thereof are rounded.

Referring to FIGS. 10A, 10B, 11A and 11B, a lower conductive layer 117is deposited over the substrate 100 having the storage openings 115. Thelower conductive layer 117 is comprised of a noble metal such as iridium(Ir), ruthenium (Ru), or platinum (Pt). In addition, the lowerconductive layer 117 may also include an adhesion layer and/or a barrierlayer as already described with reference to FIG. 3.

Such a buried layer may prevent the material of the lower conductivelayer 117 from penetrating into the mold layer 110 and the like. Whenthe lower conductive layer 117 includes the barrier layer, the oxygenbarrier pattern 108 may be omitted.

Thereafter, a photoresist layer 119 is patterned on the lower conductivelayer 117 to form a photoresist opening 120 that exposes regions of thelower conductive layer 117. Referring to FIG. 10A, the photoresistopening 120 is mesh-shaped with grooves crossing over the storageopenings 115. Thus, the remaining photoresist 119 covers portions of theupper conductive layer 117 at the inner corners of the storage opening115.

Using the patterned photoresist layer 119 as a mask, the lowerconductive layer 117 is etched to form the plurality of lower electrodes125. A portion of the etch stop layer 104 within each storage opening115 and the capping layer 112 outside of the storage openings 115 areexposed.

Each lower electrode 125 includes a respective support part 122 and arespective wall part 123. The support part covers a respective oxygenbarrier pattern 108, and the wall part 123 extends upward from thesupport part 122 along at least one sidewall of the storage opening 115.In the example of FIG. 11A, the wall part 123 extends upward along thetwo sidewalls at a corner of the storage opening 115.

In the storage opening 115 of FIG. 11A, each of four lower electrodes125 is formed over a respective one of four oxygen barrier patterns 108disposed at a respective corner of the square-shaped storage opening115. The four lower electrodes 125 are separate and electricallyisolated from each-other. In addition, a top portion of the wall part123 protrudes laterally over a portion of the capping layer 112 from aprocess (i.e., overlap) margin of a photolithography process forpatterning the lower electrodes 125.

Referring back to FIG. 9B, the sidewalls of the storage openings 115 areformed to be inclined when an isotropic (non-directional) etch processis used for patterning the storage openings 115. The degree ofinclination of such sidewalls of the storage opening 115 is determinedby a thickness of the mold layer 110, a width of the mold layer 110positioned between adjacent storage openings 115, and conditions of theetch process. In that case, the lower conductive layer 117 is patternedusing an anisotropic (directional) etch process.

Alternatively, when the sidewalls of the storage opening 116 are notsignificantly inclined, the lower conductive layer 117 is patternedusing an isotropic (non-directional) etch process. With such anisotropic etch process, the lower electrodes 125 becomes furtherseparated than defined by the pattern of the photoresist layer 119.

After formation of the lower electrodes 125, the photoresist layer 119is removed to expose the lower electrodes 125. Thereafter, a capacitordielectric 127 is conformally deposited over the substrate 100 to coverthe lower electrodes 125. Subsequently, an upper conductive layer 130 isformed on the capacitor dielectric 127.

Referring to FIGS. 12A and 12B, the upper conductive layer 130 ispatterned to form upper electrodes 130 a of the stacked capacitors. Arespective upper electrode 130 a is patterned for each of the openings115. Thereafter, an encapsulating layer (not shown) is formed over thesubstrate 100 to prevent degradation of the upper electrodes 130 a, thecapacitor dielectric 127, and the lower electrodes 125. Such anencapsulating layer is comprised of Al₂O₃, TiO₂, or a combinationthereof, in one embodiment of the present invention.

Alternatively, the upper conductive layer 130 may be patterneddifferently to form the upper electrodes 130 b or 130 c of FIGS. 5 or 7.In addition, the upper conductive layer 130 may be patterned to form theupper electrode that extends continuously through columns of openings115 using an isotropic etch process. Such an isotropic etch process isamenable for etching the upper conductive layer 130 on the non-inclinedsidewalls of the opening 115. Alternatively for inclined sidewalls ofthe opening 115, the upper conductive layer 130 is patterned using ananisotropic etch process.

Further referring to FIGS. 12A and 12B, an upper insulating layer 132 isblanket deposited over the substrate 100 having the upper electrodes 130a. The upper insulating layer 132 fills the storage opening 115 in oneembodiment of the present invention.

Thereafter, the upper insulating layer 132 is patterned to form aplurality of interconnection contact holes 133. Each interconnectioncontact hole 133 exposes a center region of the upper electrode 130 a inone embodiment of the present invention.

A respective interconnection plug 134 is formed to fill eachinterconnection contact hole 133. The interconnection 135 of FIGS. 2 and3 is further formed on the upper insulating layer 132. Alternatively, asillustrated in FIGS. 5 and 6, the interconnection contact hole 133′ andthe interconnection plug 134′ are formed over the intervening portion ofthe mold layer 110 between adjacent storage openings 115.

FIGS. 13A through 15A are top views illustrating steps for fabricatingthe planarized stacked capacitors of FIG. 8, according to an embodimentof the present invention. FIGS. 13B through 15B are cross-sectionalviews along line IV-IV′ in FIGS. 13A through 15A, respectively.

Referring to FIGS. 13A, 13B, 14A and 14B, after the lower conductivelayer 117 is conformally deposited, a respective photoresist opening120′ is formed over each opening 115. The photoresist opening 120′ has across-shaped as illustrated in FIG. 13A. Portions of the lowerconductive layer 117 exposed through the photoresist opening 120′ areetched away. In FIG. 13A, the photoresist opening 120′ exposes a portionof the capping layer 112 for a process margin of the photolithographyprocess. However, the photoresist layer 119′ covers most of the lowerconductive layer 117 on the capping layer 112.

Using the photoresist layer 119′ as a mask, the lower conductive layer117 is etched to form a preliminary lower electrode layer 118. Thepreliminary lower electrode layer 118 includes a plurality of supportparts 122 and a preliminary wall pattern 117 a. Each support part 122contacts a top surface of a respective oxygen barrier pattern 108.

The preliminary wall pattern 117 a includes a plane part formed on thecapping layer 112 and a plurality of extended parts along the sidewallsat corners of the openings 115. The lower conductive layer 117 is etchedin an isotropic (non-directional) etch when the preliminary wall pattern117 a is formed on non-inclined sidewalls of the opening 115.Alternatively, the lower conductive layer 117 is etched in ananisotropic (directional) etch when the preliminary wall pattern 117 ais formed on inclined sidewalls of the opening 115.

Thereafter, the photoresist layer 119′ is removed to expose thepreliminary lower electrode layer 118. The capacitor dielectric 127 isconformally deposited to cover the preliminary lower electrode layer118. Subsequently, an upper conductive layer 130 is formed on thecapacitor dielectric 127. A buffer insulating material 140 is formed onthe upper conductive layer 130 to fill the storage opening 115. Thebuffer insulating material 140 is comprised of silicon dioxide (SiO₂) inone embodiment of the present invention.

Referring to FIGS. 15A and 15B, the buffer insulating material 140, theupper conductive layer 130, the capacitor dielectric 127, and thepreliminary lower electrode layer 118 are planarized in an CMP (chemicalmechanical polishing) process until the capping layer 112 is exposed.The remaining lower electrodes 125′, the capacitor dielectric 127 a, theupper electrode 130 a′, and the buffer insulating material 140 a arecontained within the opening 115. Alternatively, when the upperconductive layer 130 fills the storage opening 115, the bufferinsulating material 140 is omitted.

Each lower electrode 125′ in FIG. 15B includes a respective support part122 that covers a respective oxygen barrier pattern 108. Each lowerelectrode 125′ includes a respective wall part 123′ that extends upwardfrom the support part 122 along sidewalls at a respective corner of thestorage opening 115. Further referring to FIG. 15B, an upper insulatinglayer 132′ is deposited over the substrate 100. An encapsulating layer(not shown) may also be formed as part of the upper insulating layer132′. Such an encapsulating layer is comprised of Al₂O₃, TiO₂, or acombination thereof in one embodiment of the present invention.

Thereafter in FIG. 15B, the upper insulating layer 132′ and the bufferinsulating material 140 a are patterned to form an interconnectioncontact hole 133″ to expose a center region of the upper electrode 130a′. An interconnection plug 134″ is formed to fill the interconnectioncontact hole 133″. In addition, an interconnection 135″ as illustratedin FIG. 8 is further formed on the upper insulating layer 132′.

FIG. 16 is a top view of stacked capacitors formed within an opening 215having a groove shape according to another embodiment of the presentinvention. FIG. 17 is a cross-sectional view along line V-V′ in FIG. 16,and FIG. 18 is an isometric view of lower electrodes of the stackedcapacitors of FIG. 16.

Referring to FIGS. 16, 17, and 18, a lower insulating layer 202 and anetch stop layer 204 are deposited on a semiconductor substrate 200. Aplurality of contact holes 205 are formed through the etch stop layer204 and the lower insulating layer 202 to expose regions of thesubstrate 200. The contact holes 205 are arranged in rows and columns. Arespective contact plug 206 and a respective oxygen barrier pattern 208fill each contact hole 205.

A mold layer 210 is deposited to cover the etch stop layer 204 and theoxygen barrier pattern 208. A capping layer 212 is deposited on the moldlayer 210. The etch stop layer 204 is comprised of an insulatingmaterial having etch selectivity from the mold layer 210.

Parallel groove-shaped storage openings 215 are formed through thecapping layer 212 and the mold layer 210 to expose the oxygen barrierpatterns 208 along a column direction, in one embodiment of the presentinvention. In the embodiment of FIG. 16, each of two columns of exposedoxygen barrier patterns 208 are disposed adjacent to a respective one oftwo sidewalls of the storage opening 215. Such sidewalls of the opening215 may be inclined with a distance between the sidewalls increasingupward in the opening 215.

A respective lower electrode 225 is patterned over each oxygen barrierpatterns 208 in the storage opening 215. Each lower electrode 225includes a respective support part 222 and a respective wall part 223.The support part 222 contacts a respective oxygen barrier pattern 208,and the wall part 223 extends upward from the support part 222 along asidewall of the opening 215.

A pair of lower electrodes 225 is formed on opposite sidewalls of theopening 215 to face each other, in one embodiment of the presentinvention. A top portion of the wall part 223 extends laterally over aportion of the capping layer 212. The lower electrodes 225 within eachstorage opening 215 are separate and electrically isolated from eachother. In addition, the lower electrodes 225 disposed in differentstorage openings 215 are separate and electrically isolated from eachother.

The lower electrodes 225 are comprised of a noble metal such as iridium(Ir) or ruthenium (Ru) in one embodiment of the present invention. Inaddition, the lower electrodes 225 may include an adhesion layer and/ora barrier layer, similarly as described with reference to FIGS. 3, 6,and 12B.

After formation of the lower electrodes 225, a capacitor dielectric 227is conformally deposited to cover the lower electrodes 225.Subsequently, an upper electrode 230 a is formed on the capacitordielectric 227 over the lower electrodes 225. Each upper electrode 230 amay cover all of the lower electrodes 225 in the cell block (not shown)of a memory device. Alternatively, each upper electrode 230 a covers onestorage opening 215 as illustrated in FIG. 16. When the capacitordielectric 227 is comprised of a ferroelectric material for using thestacked capacitors in a ferroelectric memory device, the upper electrode230 a forms a plate line of the ferroelectric memory device.

Alternatively similar to FIG. 6, the upper electrode 230 a may be formedover an intervening portion of the mold layer 210 between adjacentstorage openings 215. Alternatively similar to FIG. 7, each upperelectrode 230 a may be formed over a column of lower electrodes 225along one sidewall of the groove-shaped opening 215.

Alternatively as illustrated in FIG. 19, each lower electrode 230 a iselectrically isolated to cover an array of four adjacent lowerelectrodes 225 within the groove-shaped opening 215. In that case, aplurality of upper electrodes 230 b is formed along each groove-shapedopening 215.

An upper insulating layer 232 is blanket deposited on the substrate 200to cover the upper electrodes 230 b. Each interconnection plug 234 isformed through the upper insulating layer 232 to contact a respectiveupper electrode 230 b. Interconnections 235 are arranged parallel on theupper insulating layer 232, and each interconnection is coupled to acolumn of the interconnection plugs 234.

With such stacked capacitors of FIGS. 16, 17, 18, and 19, eachgroove-shaped storage opening 215 is formed to be relatively wide forholding a plurality of stacked capacitors therein. With such a largeopening 215, the capacitor dielectric 227 may be formed with arelatively large thickness to reduce leakage current between the lowerand upper electrodes of the stacked capacitors and to preserve thepolarization hysteresis of the capacitor dielectric 227 comprised of aferroelectric material. Furthermore with such a large opening 215, theupper electrode 230 a overlap the lower electrodes 225 even for largethickness of the capacitor dielectric 227.

Additionally with such a large opening 215, the height of the wall part223′ of the lower electrodes 225 is further increased within acceptableaspect ratio of the opening 215 for in turn increasing area and thuscapacitance of the stacked capacitors. Overlap between the lowerelectrode 225 and the upper electrode 230 a over a portion of thecapping layer 212 further increases area and thus capacitance of thestacked capacitors.

FIG. 20 is a cross-sectional view along line V-V′ in FIG. 16 withplanarization of the stacked capacitors, according to another embodimentof the present invention. Referring to FIG. 20, each lower electrode225′ includes a respective support part 222 and a respective wall part223′ that is contained within the opening 215. Similar to FIG. 17, acapacitor dielectric 227 is deposited on the lower electrodes 225′ andan upper electrode 230 a′ is deposited on the capacitor dielectric 227.A buffer insulating material 240 a is blanket deposited to fill theopenings 215.

Thereafter in FIG. 20, the buffer insulating material 240 a, the upperelectrode 230 a′, the capacitor dielectric 227, and the lower electrodes225′ are planarized in a CMP (chemical mechanical polish) process. Thus,the buffer insulating material 240 a, the upper electrode 230 a′, thecapacitor dielectric 227, and the lower electrodes 225′ are contained tobe electrically isolated within each storage opening 215.

In an alternative embodiment, the upper electrode 230 a′ fills thestorage opening 215. In that case, the buffer insulating material 240 ais omitted. An encapsulating layer (not shown) may be disposed as partof the buffer insulating material 240 a to cover the electrodes 225′ and230 a′ and the capacitor dielectric 227. Such an encapsulating layerprevents degradation of the electrodes 225′ and 230 a and the capacitordielectric 227.

In the embodiment of FIG. 20, the lower electrodes 225′, the capacitordielectric 227, the upper electrode 230 a′, and the buffer insulatingmaterial 240 a are planarized to be contained within the opening 215.Such a resulting flat step coverage allows for easier subsequentdeposition of integrated circuit materials thereon for improvingfabrication yield.

FIGS. 21A and 22A are top views illustrating steps for fabricating thestacked capacitors of FIG. 16 according to an embodiment of the presentinvention. FIGS. 21B and 22B are cross-sectional views along line VI-VI′in FIG. 21A and 22A, respectively.

Referring to FIGS. 21A and 21B, the lower insulating layer 202 and theetch stop layer 204 are sequentially deposited on the substrate 200. Arespective contact plug 206 with a respective oxygen barrier pattern 208thereon fills each contact hole 205 formed through the etch stop layer204 and the lower insulating layer 202 as similarly described above forother embodiments of the present invention.

Thereafter, the mold layer 210 and the capping layer 212 aresequentially deposited over the substrate 200. The capping layer 212 andthe mold layer 210 are patterned to form the storage openings 215 havinga groove-shape and exposing two adjacent columns of the oxygen barrierpatterns 208. The storage openings 215 are parallel to each other. Thesidewalls of the openings 215 are inclined with a width of the storageopening 215 gradually increasing upward.

A lower conductive layer 217 is conformally deposited over the substrate200 and within the storage openings 215. The lower conductive layer 217is comprised of material(s) as described above for the other embodimentsof the present invention. Referring to FIGS. 22A and 22B, the lowerconductive layer 217 is patterned to form a plurality of lowerelectrodes 225 each contacting a respective oxygen barrier pattern 208.

Each lower electrode 225 includes a respective support part 222 and arespective wall part 223. The support part 222 contacts a respectiveoxygen barrier pattern 208, and the wall part 223 extends upward fromthe support part 222 along a sidewall of the storage opening 215. Thelower electrodes 225 are separate and electrically isolated from eachother.

For patterning the lower conductive layer 217, an isotropic(non-directional) etch process is used when the lower electrodes 225 areformed on a non-inclined sidewall of the opening 215. Alternatively, ananisotropic (directional) etch is used when the lower electrodes 225 areformed on an inclined sidewall of the opening 215.

Thereafter, a capacitor dielectric 227 is conformally deposited over thesubstrate 200 to cover the lower electrodes 225. Subsequently, an upperconductive layer 230 is formed on the capacitor dielectric 227. Theupper conductive layer 230 is patterned to form upper electrodes 230 aof FIGS. 16 and 17. The lower electrodes 225, the capacitor dielectric227, and the upper electrode 230 a form the stacked capacitors of anembodiment of the present invention. After the upper electrode 230 a isformed, an encapsulating layer (now shown) is formed over the substrate200 to prevent degradation of the stacked capacitors.

The upper conductive layer 230 is patterned to form the upper electrodessimilarly as described in the above embodiments of the presentinvention. An isotropic etch process is amenable for etching the upperconductive layer 230 on non-inclined sidewalls of the opening 215.Alternatively for inclined sidewalls of the opening 215, the upperconductive layer 230 is patterned using an anisotropic etch process.Thereafter, an upper insulating layer 232, interconnection plugs 234,and interconnections 235 are formed similarly as described in the aboveembodiments of the present invention.

FIGS. 21A and 23A are top views for illustrating fabrication of thestacked capacitors of FIG. 20, according to another embodiment of thepresent invention. FIGS. 21A and 23B are cross-sectional views alonglines VI-VI′ and VII-VII′ in FIGS. 21A and 23A, respectively.

Referring to FIGS. 21A, 21B, 23A and 23B, a lower conductive layer 217is conformally deposited over the substrate 200 having the storageopenings 215. The lower conductive layer 217 is patterned to form thepreliminary lower electrode layer 218 that initially remains over thecapping layer 212. The preliminary lower electrode layer 218 alsoincludes a plurality of support parts 222 and a preliminary wall pattern217 a connected to the support parts 222. The temporary wall pattern 217a includes a plane part formed on the capping layer 212 and a pluralityof extended parts that extend downward from the plane part along aninner sidewall of the storage opening 215 to be connected to a supportpart 222.

For forming the preliminary lower electrode layer 218, an isotropic etchprocess is amenable for non-inclined sidewalls of the opening 215.Alternatively for inclined sidewalls of the opening 215, the lowerconductive layer 217 is patterned using an anisotropic etch process.

After formation of the preliminary lower electrode layer 218, acapacitor dielectric 227 is deposited conformally on the substrate 200to cover the preliminary lower electrode layer 218. Thereafter, an upperconductive layer 230 is formed on the capacitor dielectric 227. Theupper conductive layer 230 may be deposited conformally. A bufferinsulating material 240 is formed on the upper conductive layer 230 tofill the storage opening 215.

Subsequently, the buffer insulating material 240, the upper conductivelayer 230, the capacitor dielectric 227, and the preliminary lowerelectrode layer 218 are planarized until the capping layer 212 isexposed. With such planarization, lower electrodes 225′, a capacitordielectric 227, an upper electrode 230 a′, and a buffer insulatingmaterial 240 a are contained within the openings 215. The preliminarywall pattern 217 a becomes separated from the planarization to form wallparts 223′ that are electrically isolated.

If the upper conductive layer 230 fills the storage opening 215, thebuffer insulating material 240 may be omitted. Alternatively, thepresent invention may be practiced with a CMP (chemical mechanicalpolish) process for planarizing the upper conductive layer 230, thecapacitor dielectric 227, and the preliminary lower electrode layer 218with or without the buffer insulating material 240 or the upperconductive layer 230 filling the opening 215.

With such stacked capacitors of the above embodiments of the presentinvention, a storage opening is formed to be relatively large forholding a plurality of stacked capacitors therein. With such a largeopening, the capacitor dielectric may be formed with a relatively largethickness to reduce leakage current between the lower and upperelectrodes of the stacked capacitors and to preserve the polarizationhysteresis of the capacitor dielectric comprised of a ferroelectricmaterial. Furthermore with such a large opening, the upper electrodeoverlaps the lower electrodes even for large thickness of the capacitordielectric.

Additionally with such a large opening, the height of the wall parts ofthe lower electrodes are increased within acceptable aspect ratio of theopening for in turn increasing the area and thus the capacitance of thestacked capacitors. Overlap between the lower electrode and the upperelectrode over a portion of the capping layer further increases area andthus capacitance of the stacked capacitors.

The foregoing is by way of example only and is not intended to belimiting. For example, the present invention herein is described forapplication of the stacked capacitors in memory devices. However, thestacked capacitors of the present invention may also advantageously beapplied for any other types of devices using capacitors. In addition,the materials described herein or any shapes illustrated and describedherein are by way of example only. The present invention is limited onlyas defined in the following claims and equivalents thereof.

1. A plurality of stacked capacitors, comprising: an opening formedthrough at least one semiconductor material; and a plurality of lowerelectrodes patterned within the opening, wherein each of the stackedcapacitors is formed with a respective one of the lower electrodeswithin the opening.
 2. The stacked capacitors of claim 1, wherein theopening is formed through a capping layer and a molding layer.
 3. Thestacked capacitors of claim 1, wherein each of the lower electrodesincludes a respective support part disposed over a respective conductiveplug, and includes a wall part disposed along a respective portion of atleast one wall of the opening.
 4. The stacked capacitors of claim 1,wherein the opening has at least one inclined sidewall.
 5. The stackedcapacitors of claim 1, further comprising: a capacitor dielectric formedon the lower electrodes; and a upper electrode formed on the capacitordielectric.
 6. The stacked capacitors of claim 5, wherein the capacitordielectric is comprised of one of a high-K dielectric or a ferroelectricmaterial.
 7. The stacked capacitors of claim 5, wherein the upperelectrode is continuous over a plurality of openings, with each openinghaving a respective plurality of stacked capacitors formed therein. 8.The stacked capacitors of claim 5, wherein the upper electrode iscontinuous over a column of stacked capacitors formed through aplurality of openings.
 9. The stacked capacitors of claim 5, furthercomprising: an upper insulating layer formed over the upper electrode;and an interconnect plug formed through the upper insulating layerwithin the opening and coupled to the upper electrode.
 10. The stackedcapacitors of claim 5, further comprising: an upper insulating layerformed over the upper electrode; and an interconnect plug formed throughthe upper insulating layer outside of the opening over a mold layer andcoupled to the upper electrode.
 11. The stacked capacitors of claim 5,wherein the lower electrodes, the capacitor dielectric, and the upperelectrode are planarized to be contained within the opening.
 12. Thestacked capacitors of claim 5, wherein the opening is formed through acapping layer and a molding layer, and wherein the lower electrodes, thecapacitor dielectric, and the upper electrode are formed over a portionof the capping layer.
 13. The stacked capacitors of claim 1, furthercomprising: a buffer insulating layer filling the opening.
 14. Thestacked capacitors of claim 1., wherein an upper electrode fills theopening.
 15. The stacked capacitors of claim 1, wherein the opening hasa square shape, and wherein each lower electrode is disposed at arespective corner of the opening.
 16. The stacked capacitors of claim 1,wherein the opening has a groove shape, and wherein the lower electrodesare formed along sides of the opening.
 17. The stacked capacitors ofclaim 1, wherein the stacked capacitors are part of a DRAM (dynamicrandom access memory) device or a ferroelectric memory device.